Dicarbonyl compounds Hexamethylphosphoric triamide

Titanium(IV) isopropoxide, 311 a,(3-Epoxy aldehydes and ketones Fluorine-Acetonitrile, 135 Oxodiperoxymolybdenum-(pyridine)(hexamethylphosphoric triamide), 227 a,(3-Epoxy silanes Allyltriisopropylsilane, 11 m-Chloroperbenzoic acid, 76 Esters (see also Dicarbonyl compounds, Unsaturated esters)... 

The tendeney towards reaetion at the center with the maximum eleetron density inereases when dipolar non-HBD solvents are employed owing to the laek of speeifie solvation cf. solvents HCON(CH3)2 and CH3SOCH3 in Table 5-22). Thus, in the alkylation of the enolate ions of 1,3-dicarbonyl compounds, the greatest yields of the 0-alkylated isomers are obtained in hexamethylphosphoric triamide, followed by dipolar non-HBD solvents of the amide type [372-375]. 

To summarize, it can be stated that the freer the ambident anion in every respect, the larger the 0/C-alkylation ratio in the case of 1,3-dicarbonyl compounds [365]. Thus, if 0-alkylation products are desired in the alkylation of enolates, dipolar non-HBD and dissociating solvents such as A, A -dimethylformamide, dimethyl sulfoxide, or, especially, hexamethylphosphoric triamide should be used. If C-alkylation is desired, protic solvents like water, fluorinated alcohols, or, in the case of phenols, the parent phenol will be the best choice [365]. 

Oxodiperoxymolybdenum-pyridine-hexamethylphosphoric triamide, MoOj CjHsN-HMPA (MoOPH), which is prepared from molybdenum trioxide, M0O3 [531,532], hydroxylates the enolates of ketones and esters in the a position with respect to the carbonyl groups [537, 532, 533] and, in the presence of mercuric acetate, converts acetylenes into a-dicarbonyl compounds [534]. 

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See also in sourсe #XX -- [ ]

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